A cutting tool, such as a drill or twist drill, is generally comprised of a cylindrical shaft having at least one flute and land, which follow a helical angle to a forward cutting edge at the forward end of the shaft. The land has associated with it a margin and a clearance portion behind the margin. A side cutting edge is defined by the intersection of the flute with the margin of the land.
An example of a drill of this type is shown, for example, in U.S. Pat. No. 4,913,603 and U.S. Patent Application Publication No. 2008/0199268 A1. The '603 patent and the '268 patent publication describe the problem known in the technical literature as “chatter”, a problem that is experienced with a drill during the drilling process when the irregular rotational action of the drill during the drilling process results in an irregular surface structure of the boring wall. This phenomenon is due in particular to the fact that linear or spiral chip flutes are shaped into the generated surfaces of the drills to remove the chips that are formed during the drilling process. Frequently, the chip flutes on one hand and the cutting edges of the drill on the other hand are distributed symmetrically over the periphery of the drill. This symmetrical distribution has the further disadvantage that the vibrations of the drill that cause the “chatter” recur periodically during the drilling process. This periodic recurrence of the vibrations causes an increase in the amplitude of the vibrations, i.e. a “build-up” of the chatter during the drilling process. The result is that the irregularities in the side walls of the hole which is being bored, which irregularities are also called ““chatter marks”” increase, resulting in a deterioration in the quality of the boring over the length of the drilling process.
To reduce this problem, it is generally known that the minor cutting edges of the drill that are present on the drill periphery can be provided with lands. These lands are generally snug up against the inside wall of the boring and act on the drill in the manner of support fins. The '603 patent and the '268 patent publication describe that an additional measure to prevent the untrue running of the drill is the asymmetrical arrangement of the chip flutes and correspondingly of the drill cutting edges.
The present invention has been developed in view of the foregoing.